I don't know if this is of any help, but I found that it's much easier if you sing each note individually - with Simon says you don't actually need to do it as one song

so what I ended up doing is pressing "Ctrl" whilst moving the mouse in the direction for the first note, releasing "Ctrl", and repeating the process for the second+ note(s)

it meant that I didn't have to worry about the manoeuvring the mouse into the middle to avoid hitting the wrong note at all <(^_^)> also, it's pretty fast!

However, it did mean I had to be careful which direction I was moving the mouse in (because of the speed you can go at), and a slightly wrong angle means the wrong note, and a restart required...
So yeah - use "Ctrl" instead of right-clicking, and release it in-between singing each note to make your job a bit easier/faster

good luck! (it took me like, 30 tries in total, but that's because I was really tired when I was trying it, and the first 20 or so were done normally and getting to about the 4th note - the last 10 (with the new method) averaged about 6 notes

)